MFC r290911,r290912:

r290911:

Ignore EINTR from usleep(3) in try_locks(..)

NetBSD's usleep(3) only returns -1/sets errno=EINVAL when microseconds
is one million or more

Submitted by: pho
Sponsored by: EMC / Isilon Storage Division

r290912:

Integrate contrib/netbsd-tests/kernel/t_lockf.c into the FreeBSD test suite as
tests/sys/kern/lockf_test

Sponsored by: EMC / Isilon Storage Division